Continuous heating furnace



Oct. 6, 1942. w. A. MORTON 2,298,149

commilbus HEATING Ful'mAcE v Filed May 31, 1940 2 Sheets-Sheet 1 W lslzlzuToR M ATTORNEY Oct. 6, 1942 w. A. MORTON CONTINUOUS HEATING FURNACE2 Sheets-Sheet 2 Filed May 31, 1940 W I. INVE BY .gATToRNEX PatentedOct. 6, 1942 CONTINUOUS HEATING FURNACE William A. Morton, Mount LebanonTownship, I Allegheny County, Pa., assignor-to The Amslerv MortonCompany, Pittsburgh, Pa., a. corporation of Pennsylvania Application May31, 1940, Serial No. 337,988 Claims. (01. 263-) This invention relatesgenerally to heating furnaces and more particularly to heating furnacesof the type wherein articles are heated as they are continuously movedtherethrough.

In the steel industry a continuous type heating furnace is employed foruniformly heating billets,

ingots, blooms, slabs, rails and the like, to a predeterminedtemperature, preparatory to rolling or performing other operationsthereon. I

This type of furnace ordinarily contains two charge end, and second, byplacing the burners at both the charging and discharge ends with thechambers, namely, a preheating chamber and a main heating chamber. Thelatter chamber is ordinarily provided with a soaking hearth adjacent thedischarge end thereof. Th preheating chamber isomitted when the furnaceis to be used for certain types of heating.

The material to be heated continuously passes through these chambers inthe order named and each article, when discharged from the furnace,

is uniformly heated to the proper temperature for the operation that isto be performed thereon.

There are several difierent kinds of hearth structuresemployed inthe-continuous type of heating furnace art. The most common type ofhearth is a flat refractory surface over which the steel is moved as itpasses through the furnace.

The firing is wholly above the steel and the furnace is used principallyfor-the heating of thin slabs, such for instance as slabs four inchesthick.

Another type of hearth structure supports the steel on water cooledskids, permitting the application of heat both above and below thesteel. The skids form horizontal beams and are supported upon spacedpiers or refractory pillows. In some instances the flame isdirected'from a common level toward the hearth and against the 7 steelwhich acts as a division wall, causing the flame to split, one portionof the flame passing above and the other below the steel. 'Inere was nodefinite control of the quantity of fuel passing above or below thesteeland the steel resulted. The heating medium travels in the samedirection as the movement of the steel. This type of furnace is firedfrom the discharge end and the. steel becomes overheated when the rateof production is changed. Again one of the two chambers, above or belowthe steel, is always. favored,'which results in non-uniform heatdistribution, in the vertical plane.

To avoid these difficulties independent burners have been placed aboveand below the steel to insure proper heat distribution. This method offiring has been practiced in two ways, first by placing the burners atthe charging end of the poor heating of v waste gases removed at thecenter of the furnace. With this character of hearth structure it isimpossible to control the furnace atmosphere and it is difficult tocontrol th firing because the firingchambers above and below the steelare connected with one another around the ends of the steel articles.

Another character of hearth structure permits the name to travel abovethe steel in the same direction of its movement and the waste gases atthe discharge end are then circulated back under the steel and pass outthrough fiues adjacent the firing end. This method is impracticalbecause the fiame, which is above the steel, loses a greater portion ofits heat before it is drawn down under the steel, an the gases which areextensively cooled vary greatly in temperature and the top and bottom ofthe steel is not uniformly heated.

The principal object of this invention is the provision of a continuoustype heating furnace having independent firing chambers above and belowthe steel to be heated.

Another object is the provision of a continuous type heating furnacehaving independent firing chambers separated by the steel being heatedand wherein the flame propagation in both chambers is in the samedirection.

Another object is the provision of independent firing chambers in aheating furnace which are separated by the steel being heated and whichare fired separately but exhausted into a com-' mon fiue.

Another object is the provision of a continuous heating furnace having apreheating chamber and a main heating chamber and a hearth extendingtherethrough for supporting the steel to be heated which divides thepreheating and the main heating chambers in the plane of the hearth intoan upper and lower independent firing chamber.

Another object is the provision of an irregularity in the surface of thesoaking hearth for causing each successive article to directly exposeits sides to the application of heat when moved thereover.

Other objects and advantages appear in the following description andclaims. The accompanying drawings disclose a practical embodimentillustrating the principles of I this invention wherein:

furnace with the waste gases removed at the dis Fig. 1 is a sectionalview taken longitudinally of a continuous type furnace comprising thisin- VGZItiO Fig. 2 is a horizontal sectional view taken along the planeof the hearth of the furnace shown in Fig. 1.

Fig. 3 is a vertical sectional view taken alon the line 3-3 of Fig. 1.

Fig. 4 is a sectional view taken longitudinally of-another stylecontinuous type furnace employing this invention.

Referring to Fig. 1, the furnace illustrated therein is made up of twosections, the heating chamber l having an extended soaking hearth II,and a preheating chamber l2. The preheating chamber [2 is omitted whenthe furnace is employed for heating certain kinds of steel. Water cooledskids l3, which form the hearth for supporting the steel, extend throughthepreheating chamber l2 and the main heating chamber III to one end ofthe solid soaking hearth II and from the other end ofthe soaking hearthto the discharge end of the furnace. The 'ma-' terial H to be heated ischarged through the opening l5 into the preheating chamber l2 and bersI1 and It. The chamber II, which is above the steel, is enclosed by theroof I! and the side walls 20. The steel charge ll forms the bottom ofthis chamber. The chamber 18 is formed by the steel H and the-floor 2i,which is below the plane of the hearth, and the continuous verticalwalls 22 which rise from the floor 2i and support the outermost skids l3as shown in Figs. 2 and 3. The walls 22 are closely adjacent the sidewalls 2| of the furnace and extend from the end wall 23 of thepreheating chamber to the intermediate transverse-furnace wall 2 at theend of the soaking hearth. Thus the lower heating chamber i8 is roofedin by the materials being heated. The intermediate skids I; aresupported on the short continuous walls 25 in the preheating chamber andon the piers 26 within the main heating chamber Ill.

The rear wall 26' of the furnace is provided 2 with two rows of burners21 and 28 for firing the chambers l1 and II respectively. These burnersare supplied with fuel carried by the conduits and with preheated aircarried by the ducts 3i and 32 respectively. As shown in Figs. 2 and 3,three burners 28 are arranged to flre the chamber 18 between thevertical walls 22, while the space outside of the walls 22 or betweenthe walls 22 and each of the side furnace walls 20 is fired with theburners 29. The flame from the latter burners heat the under side of theends of the articles and a portion of the products of combustion fromthese flames may travel up around the ends of the steel articles intothe chamber The burners of the preheating chamber are ordinarily of lesscapacity than those of the main heating chamber and may be supplied withpreheated air by a branch line from the conduit ii. The air induced bythe pressure of fuel in these burners and the slight infiltration of airthrough the charging opening is utilized in supporting the combustion ofthe fuel. Combustion is substantially complete before the gases reachthe main chamber Iii and these burnt gases thereafter blanket the steelas they travel to the exhaust flues at the discharge end of the furnace.In this manner the atmosphere surrounding the steel may be controlled toprevent excess oxidation and/or decarburization of the steel. Radiantheat energy from the hottest part of the flames issuing from the mainburners 21 and 28 is thus prevented from being applied directly on thesteel.

The preheated steel is thus subjected to radiant heat energy from thefurnace surfaces and the flames in both the upper and lower heatingchambers I1 and I8 which must pass through the products of combustionblanketing the steel. If the steel is subjected to the direct radiationof the flames, which is the present practice, the

steel is heated in streaks. Streak heating is detrimental in rolling andother mill operations. This disadvantage is overcome by diffusing theradiant heat energy as it passes through the blanketing layer of theproducts of combustion from the preheating chamber. When the combustionof the main burner flames is substantially complete the products ofcombustion from both the preheating flames and the main burner flamescombine and continue to blanket the steel as they pass on through thefurnace. In this manner the atmosphere adja'ent the steel is controlledand prevents excess oxidation and decarburization of the steel.

The radiant heat energy being diffused as it passes through theblanketing products of combustion thereby provides a uniform temperaturethroughout each article of steel, which eliminates the detrimentaleffects due to direct heating from initial flame combustion. .Again theefficiency of the heatexchang'e is increased by the extended flamelength and the location of the hottest heating areas may be accuratelydetermined.

The hot waste gases passing from the chamber is and from the sideburners 2s and :1 below the plane of the hearth, as shown in Fig. 2,flow up over the transverse wall 38 and down through the flues ll whichare connected at their lower ends with the transverse flue II.

The hot waste gases passing from the chamber ll above the planeof'the'hearth continue to blanket the steel, as it passes over thesoaking hearth II, and are drawn down past the discharge opening intothe flue's 42 which are connected at-their lower end to the transverseflue 43. This prevents the entrance of cold air into the furnacechamber,'as any infiltration of air through the discharge door is drawndown directly into the flues. Y 4

The flames produced by the burners '23 travel rearwardly over thesoaking hearthv ii substantially parallel with the steel until thevelocity of the burning gases is reduced-"to such an extent that thedraft induced by the fines 4|. in the vicinity of the burners 3'2,reverses the path .of movement. of the products of combustion.

Combustion issubstantially complete before the gases are redirected. andmingle with the gases blanketing the steel. Thus the flames in the vdischarge end of the furnace heat the steel by radiant heat energy in amanner similar to that described above and the hottest portion of theseflames is along their initial path. Thus the steel is protected by theproducts of combustion during the most critical periods. of the heatingprocess.

The collecting flues 4| and 43 are connected by face of the soakinghearth ll adjacent the discharge end. As the steel articles are movedover this portion of the hearth the sides become exthe flue 44 tothe'recuperator 45. The waste the main burners are shut. down. Duringmill .delays the movement of the steel through the furnace is stoppedand the furnace temperature rises. The automatic controls then operateto reduce the firing rate of the main burners until this rate is reducedto a predetermined quantity at which time an automatic, transfer iseffected for shutting down the main burners and firing the burners 33.These burners are then automatically regulated by the same controlmechanism to maintain the steel on the soaking hearth at its properrolling temperature. When the steel is again taken from the soakinghearth for rolling and new steel is supplied to the chargingend theautomatic controls are again actuated by the temperature of the furnaceto transfer the firing back to the main burners for normal operatingconditions.

The temperature of the furnace is controlled automatically by a fluidsystem actuated by the pyrometer 49 which measures the temperature-of Ithe waste gases passing out of the furnace and down through the flue 42,for the purpose of control. The temperature of these gases have a directrelation to the temperature of-the steel which they blanket. Thistemperature controller regulates the quantity of air delivered by theblower 50 to the recuperator and the fuel delivered to the burners is inturn fed in proportionate quantities with respect to the quantity of airsupplied. The pressure of the furnace is automatically regulated by thedamper 5| in the flue 46. This damper is controlled by the motor 52actuated by a mechanism which receives pressure impulses from thefurnace. These impulses are preferably taken from the soaking chamber.The soaking hearth ll may be provided with some means for verticallyshifting the individual articles during their travel over the soakinghearth. Such a movement exposes the sides of the articles permittingthem to receive the same heat treatment as the normally exposedsurfaces. Thus the body and the surfaces of the articles are heateduniformly and provide improved material for rolling or other operations.

The articles may be vertically shifted by a mechanically operateddevice, manually, or by'providing elevations. or'depressions in thesurface of the soaking hearth. The latter provides the simplest form forarticles which are substantially square or rectangular in cross section.It may be found preferable to vertically shift the whole of the articleat one time as some articles may deviate sideways due to theirparticular shape if one end is raised or lowered.

In s. 1 and 2 a transverse depression 53 and a hump or elevation 54 isshown in the surposed to products of combustion. These surfaceformations may be constructed to roll each article completely over orthrow it on its side. Again a plurality of these transverse surfaces maybe provided along the soaking hearth and properly spaced from oneanother to shift several articles so that their sides are exposed justat the time the leadingarticle is discharged from the furnace.

In the furnace structure shown in Fig. 4, the

burners 21 and 28, which fire the upper and lower independent heatingchambers I1 and I8 respectively, are faced in the opposite direction tothat shown in Fig. 1. The preheating chamber I2 is not provided withburners and the products of combustion from both of the chambers I1 andI8 flow through the upper and lower levels of the preheating chamber l2,down through the vertical flues 40, past the charging door l5, and alongthe horizontal-flue 44 to the recuperator and out the flue 46 to thestack. The flames from r the burners '33'project into the furnacechamber over the soaking hearth H until the velocity of the gases isreduced sufliciently to redirect them back over the'steel, in the samemanner as that described above. These gases are then discharged thrdughthe flues 42 and the damper controlled auxiliary stack 55.

J'In each of the structures illustrated in Figs. 1 and 4 the two firingchambers, above and below the steel, extend from the-preheatingchamber"through the main heating chamber. These chambers are-structurallyindependent from one another except for the commonpartit-ion formed bythe steel being heated as illustrated. These firing chambers may beexhausted to the same or separate flues. However this does not affectthe efficient operation of each of these firing chambers.

Ordinarily the furnace is constructed so that the ends of the steelarticles are supported on the outer hearth skids l3. However thisfurnace can be successfully operated by placing vtwo shorter articles ofsteel in longitudinal alignment with their adjacent ends touching. Onlyfour hearth skids are shown in Fig. 2 but more may be added if shorterlengths of steel are to be heated. If this is done it may be necessaryto relocate the main burners 28 and 29 and the preheating burners 36 and31 so that the flames will not play directly on the piers.

I claim: 1. A continuous furnace for heating billets and the likecomprisingrupper and lower interior portions which during the operationof the furnace are separated into distinct and non-communicatingchambers by the row of billets passing through the furnace on spacedapart skids supported by continuous solid walls, and independentlycontrolled separate means for introducing heating flames into andwithdrawing the products of combustion from each of said chambers toheat the billets from above and below.

2. A continuous furnace for heating billets and the like comprisingupper and lower interior portions which during the operationof thefurnace are separated into distinct and non-communicating chambers bythe row' of billets passing through the furnace on spaced apart skidssupported by continuous solid walls, and independently controlledseparate means for introducing heating flames into and'causing them totravel in the same direction in both chambers for substantially the fulllength thereof longitudinally of the furnace to heat the billets fromabove and below.

3. A continuous furnace for heating billets and the like comprisingupper and lower interior portions which during the operation of thefurnace are separated into distinct and non-communicating chambers bythe row of billets passing through the furnace, and separate means forintroducing heating flames into both chambers and. causing them totravel in the direction of the travel of the billets for substantiallythe full length of said chambers.

4. A continuous furnace for heating billets and the like comprising apreheating portion and a heating portion connected thereto and throughwhich the billets pass in turn, the upper and lower interiors of saidportions being divided by the row of billets being heated which slide onspaced apart skids supported by continuous solid walls to form separateand non-communicating chambers longitudinal of the furnace above andbelow the row of billets, and independently controlled means for theseparate introduction of heating flames into each of said chambers.

5. A continuous furnace for heating billets and the like comprising apreheating portion and a heating portion connected thereto and throughwhich the billets pass in turn, the upper and lower interiors of saidportions being divided by the row of billets being heated which slide onspaced apart skids supported by continuous solid walls to form separateand non-communicating chambers longitudinal of the furnace above andbelow the row of billets, and independently controlled separate meansfor introducing heating flames into andcausing them to travel in thesame direction in both chambers longitudinally of the furnace to heatthe billets from above and below for substantially the full length ofsaid chambers. v

6. A continuous furnace for heating billets and the like comprising apreheating portion and a heating portionconnected thereto and throughwhich the billets pass in turn, the upper and lower interiors of saidportions being divided by the row of billets being heated which slide onspaced apart'skids supported by continuous solid walls to form separateand non-communicating chambers longitudinal of the furnace above andbelow the row of billets, and separate means for introducingheating-flames into both chambers and causing them to travel in thedirection of the travel of the billets for substantially the full lengthof said chambers.

7. In a continuous furnace for heating billets and the like having sidewalls and roof, a pair of longitudinally disposed continuous inner wallswithin the furnace and spaced from the side walls, skids carried by thetops of said inner walls, the

I billets traveling along said skids in their passage independentlyintroducing and controlling heat- I ing flames into the furnace aboveand below the billets.-

9. A continuous furnace for heating billets and v the like comprisingupper and lower interior portions which during the operation of thefurnace are separated into two distinct and non-communicating chambersby the row of billets passing through the furnace on spaced apart skidssupported by continuous solid walls, and independently controlledseparate means for introducing heating flames into both chambers andcausing the same to travel in the direction opposite to that of thetravel of the billets for substantially the full length of saidchambers.

10. A continuous furnace for heating billets and thelike, comprising apreheating portion and a heating portion through which the billets passin turn, a pair of continuous inner walls longitudinal of the interiorof the furnace and spaced from each other and from the side walls of thefurnace and along the tops of which inner walls the billets move forminga continuous partition completing a chamber beneath the billets andbetween the inner walls and which extends I through the preheating andheating portions of the furnace, said walls and billets formingnoncommunicating independent upper and lower preheating and heatingchambers, and independently controlled means for the separateintroduction of heating flames into the furnace above and below thebillets and causing the same to travel in the direction opposite to thatof the travel of the billets for substantially the full length of'saidchambers.

11. A continuous furnace for heating billets and the like comprising aheating portion which when the furnace is in operation is divided by therow of billets passing through the furnace on spaced apart skidssupported by continuous solid walls into independent andnon-communicating upper and lower heating chambers. a soaking hearthadjacent the discharge end of the furnace over which the billets pass,independently controlled means for introducing heating flames into eachof said heating chambers and causing them to travel in-the directionopposite to that of the tudinal ofthe interior of the furnace and spacedtravel of the billets for substantially the full length of saidchambers, means for introducing heating flames adjacent the dischargeend of the furnace, and means for redirecting the products of combustionfrom said flames toward the discharge end of the furnace and between theflames and the billets. t

12. A continuous furnace for heating billets and the like comprisingupper and lower interior portions which during the operation of thefur-- nace are separated into distinct and non-communicating chambers bythe row of billets passing through the furnace, separate means forintroducing heating flames into both chambers and causing them to travelin the direction of the travel of the billets for substantially the fulllength of said chambers, and separate means for discharging the productsof combustion from each chamber.

and heating chambers, independently controlled ;3. A continuous furnacefor heating billets and the like comprising upper and lower interiorportions which during the operation of the furnace are separated intodistinct and non-communicating chambers by the row of .billets passingthrough the furnace, separate means for introducing heating flames intoboth chambers and causing them to travel in the direction of the travelof the' billets for substantially the full length of said chambers,separate means for discharging the products of combustion from eachchamber, and means for controlling the rate of withdrawal of theproducts of combustion through said discharge means.

14. A continuous furnace for heating'billets and the like, comprisingapreheating portion and a heating portion through which the billets passin turn, a pair of continuous inner walls longitudinal of the interiorof the furnace and spaced from each other and from the side walls of thefurnace and along the tops of which-inner walls the billets moveforminga continuous partition completing a chamber beneaththe billetsand between the inner walls and which extends through the preheating andheating portions of the furnace, said walls and billets formingnon-communmeans for introducing heating flames into the furnace aboveand below the billets, and separate means for discharging the productsof combustion from each chamber.

15. A continuous furnace for heating billets and 'the like, comprising apreheating portion and a heating portion through which the billets passin turn, a pair of continuous inner walls longitudinal of the interiorof the furnace and spaced from each' other and from the side walls ofthe furnace and along the tops of which inner walls the billets moveforming a continuous partition completing .a chamber beneath the billetsand between the inner walls and which extends through the preheating andheating, portions of the furnace, said walls and billets formingnoncommunicating independent upper and lower preheating and heatingchambers, means for introducing heating flames into the furnace aboveand below the billets, separate means for discharging the products ofcombustion from each chamber, and means for controlling the rate oficating independent upper and lower-preheating withdrawal of theproducts of combustion through said discharge means.

' 'wnLrAMA. MORTON.

